Scraper blade and process of hardening the same



y 7, 1930. w. B. BRONANDER 1,760,630

SCRAPER BLADE AND PROCESS OF HARDENING THE SAME Filed May 17, 1928 0' 7 N N V INVENTOR ATTORNEY V Patented May 27, 1930 UNIT-ED s'r W l. HELM B. IBRONANDER, OE MONTCLAIR, NEW JERSEY, ASSI GNDB IO-STANDARD IO- BACCO STEMMJER GOMP, A CQBEUEATION 9F mm semen BLADE n rnocnss or Application filed May 17,

This invention relates to scraper blades and a process of hardening the same, and is particularly applicable to the blades used as inserts on the beater drums of tobacco stemmers and similar machines.

Heretofore, in machines of this type, it has been found difiicult to provide insert blades having edges sufficiently hard and permanent to resist undue wear caused'by the grit in the 1 tobacco leaves. Blades made entirely of hardened steel have been unsatisfactory because they are brittle and cannot be straightened. Also blades having the working edge only hardened, have likewise proved unsatisfactory because, due to unequal internal strains, the blade warps; moreover, the hardened edge tends to round off at the corners. Another ditficulty encountered in of this typemaking blades for machines has been in making the blades in the same machine 'uniform. Lack of uniformity causes uneven wear and hence uneven operasharpening edges hardened where the wear- :0 is greatest. With this andother objects not specifically mentioned in view, the invention consists in certain constructions and combinations which will be hereinafter fully described and then specifically set forth in the ap nded claims. 7

' the accompanying drawings:

Fig. 1 is a side elevation of one of the blades used in a heater drum of tobacco stemmers;

Fig. 2 is an end elevation showing a bundle of blades constituting one unit ready for hardeningb the'im roved process: I 7 Fig. 3 is e si e elevation of the blade unit after notching of the blades; and Fig.4 is an enlarged view showing the comtobacco stemmer.

In carrying-the invention into effect, there is provided a blade of substantial thickness pleted blades as attached to the drum of the meme "rm s 1928. Serial No. 2?8,336.

said edge, portions of the edge being cut away to form a working edge having hardened corners and a relatively soft central portion. Preferably a series of notches forreceiving tobacco stems are cut in said edge so that the partsof the edge engaging the stems have said hardened corners and relatively soft central portions. The process used in producing a set of these blades consists in providing a plurality of blades, covering the surfaces thereof, except the edge portions to be hardened, temporarily securing said blades together in spaced relation to orin a single unit and subjecting the unit to a surface hardening operation. In the best mode of 65 carrying out the invention, the edges of said blades subjected to the surface hardening operations are cut away to provide a working edge having hardened corners and a relatively soft central portion. The method and means above referred to may be widely varied in construction within the scope of the claims, for the particular method and means selected to illustrate the invention is but one of manypossible embodimentsof the same. The inventiomtherefore, is not to be restricted to the precise details of the structure shown and described. V

Referring to the drawings, a number of blades 5 of substantial thickness at their edge portions 6, which in the present embodiment I are of high carbon steel, such as tool steel, are assembled in a unit having the spacers 10 between the successive blades, the blades and s aces being held together between the cover p ates ll'by the bolts 12 passing through the holes 9 of the plates. The number of blades in the stack is equal to the number required for a complete set of blades for the stemming machine,'so that every blade of the set will get exactly the same treatment, with the result that any wear will uniformly affect all of the blades. The acers 10 and the cover plates 11 are made 0 such width as to cover all the side surfaces of the blade, except two 0 posite longitudinal marginal portions of equalwidth and the edge ortions thereof, the surfaces of which are to hardened.

In the method selected to illustrate the inheit, more or less, for 15 or 20 minutes.

tassium cyanide, inwhich it is heated\to a temperature of around 1500 degrees Fah'i'snis then exposed to air of ordinary room temperature for a very short time, 20 or 30 seconds, to normalize the steel, after which it is quenched in oil. This will result in a th1n hardened surface portion or skin on the exposed parts of the blade. Other methods of hardening the surface portions of the blade may be used. For instance, blades of low car-. bon, or machine steel, may be utilizedand the parts which it is desired to harden, may be surface carbonized, whereby subsequent hardening will result in hardening the carbonized surface only. The exposed edge portions of the blades, after being subjected to the hardening operation, or to an essential part thereof, have notches 7 out therein, as shown in Figs. 3 and 4.

For this purpose, the blades may be disassembled from the unit' and the notches cut out in any suitable way, or the blades may be notched while in the unit, as shown in Fig. 3. The notches of each successive blade are offset to give a spiral arrangementof notches, when the blades are assembled on the drums of the stemmer machine.

As will be seen from Fig. 4, 'showin the blades as mounted on the holder 8 of the rum of the stemmer machine, the notches 7 cut in the edge of the blade 5 will cut away the hardened surface portion of the edge 6 to form a stem engaging edge parts having hardened corners 13" formed by the hardened surfaces 13, and a relatively soft central portion 7 As shown in Fi 4, the scraping operation of the blade on t e stem of the tobacco leaf will result in this softer central portion of the notched edge bein washed away or hollowed out, leaving the t in edges of the hardened surface (portions 13 exposed, thus rendering the bla es self sharpening by maintaining hard sharp corners on the stem-engaging edges of the blades.

It is noted that by hardening equal widths I v at the mar 'ns of the blades, the strains caused by shrinkmg of the blades in cooling will be neutralized. The soft center also serves to neutralize such strains and because only thin surface portions of the blades are hardened, the blades can be straightened without dan er of breaking them,

at is claimed is:

said edge, portions of the edge being cut away to form a working edge havlng hardened corners and a relatively soft central portion, said blade being rovided with similar marginal surfaces simllarl located along the opposite edge of said bla e to prevent warping.

3. An insert for tobacco stemmers compris ing a case hardened blade having an edge portion of substantial thickness, and a series of notches for receiving the tobacco stems cut in said edge portion so that the partsof the edge engaging the stems have hardened corners and relatively soft central portions.

4. An insert for tobacco stemmers comprising a blade of substantial thickness along one edge and having hardened marginal surfaces one on each side ofthe blade and extending along said edge, said blades being provided with similar marginal portions similarly located along the opposite edge of the bladeto prevent warping, the former edge having notches out therein to receive the stem, so that the parts of theedge engaging the stems have hardened corners and relatively soft central portions.

In testimony whereof, I have signed my name to this s ecification.

WIL l-IELM B. BRONANDER.

1. A self sharpening scraper element, com- I prising a blade of substantial thickness along one edge having hardened marginal surfaces I on each side of said blade and extending along said edge,'portions of the ed being cut away to form a working edge aving hardened corners and a relatively soft central portion.

2. A self sharpening scraper element, comprising a blade of substantial thickness along one edge having hardened marginal surfaces on each side of said blade and extending along 

